Projection type optical display system

1. A projection type optical display system comprising: a light source; at least one liquid crystal panel for modulating light that has been emitted from the light source; and a projection optical device for projecting the light that has gone out of the at least one liquid crystal panel, wherein the liquid crystal panel includes: a liquid crystal layer; a first polarizer and a second polarizer, which are provided on the light incoming side and the light outgoing side of the liquid crystal layer, respectively; a first uniaxial optical compensator, which is provided between the liquid crystal layer and the first polarizer; a first biaxial optical compensator, which is provided between the first uniaxial optical compensator and the first polarizer; and a second biaxial optical compensator, which is provided between the liquid crystal layer and the second polarizer, wherein if an index ellipsoid of the first and second biaxial optical compensator has a, b and a axes as principal axes and if principal refractive indices on the a, b and a axes are na, nb and no, respectively, the c axis is substantially parallel to a normal to a major surface of each said biaxial optical compensator, the a and b axes are defined on the major surface of the biaxial optical compensator, and nb>nc>na is satisfied.

2. The optical display system of claim 1 , wherein if an index ellipsoid of the first uniaxial optical compensator has a, b and c axes as principal axes and if principal refractive indices on the a, b and c axes are na, nb and nc, respectively, the a axis is substantially parallel to a normal to a major surface of the first uniaxial optical compensator, the a and b axes are defined on the major surface of the first uniaxial optical compensator, and na=nb>nc is satisfied.

3. The optical display system of claim 1 , wherein an c axis of the first and second biaxial optical compensators defines a tilt angle θ with respect to a normal to a major surface.

4. The optical display system of claim 3 , wherein the tilt angle θ defined by the c axis of the first and second biaxial optical compensators with respect to the normal to the major surface is greater than 1 degree but smaller than 20 degrees.

5. The optical display system of claim 1 , wherein an c axis of the first uniaxial optical compensator defines a tilt angle θ with respect to a normal to a major surface.

6. The optical display system of claim 5 wherein the tilt angle θ defined by the c axis of the first uniaxial optical compensator with respect to the normal to the major surface is greater than 1 degree but smaller than 20 degrees.

7. The optical display system of claim 1 , wherein a total retardation of the first and second biaxial optical compensators, which is given by d 2 t ·Δnab (where Δnab=nb−na and d 2 t is a total thickness of the first and second biaxial optical compensators), satisfies 200 nm<d 2 t ·Δnab<400 nm, and wherein another total retardation of the first and second biaxial optical compensator, which is given by d 2 t ·Δnac (where Δnac=nc−na), satisfies 100 nm<d 2 t ·Δnac<200 nm.

8. The optical display system of claim 1 , wherein a retardation of the first uniaxial optical compensator, which is given by d 1 ·Δnac (where Δnac=nc−na and d 1 is a thickness of the first uniaxidal optical compensator), satisfies 400 nm<−d 1 ·Δnac<700 nm.

9. The optical display system of claim 1 , further comprising three liquid crystal panels including the at least one liquid crystal panel, wherein the light source emits three light rays in three colors falling within mutually different wavelength ranges, and wherein the light rays in the three colors are incident onto, and modulated by, the three liquid crystal panels, respectively.

10. The optical display system of claim 1 , wherein the light source emits three light rays in three colors falling within mutually different wavelength ranges, and wherein the light rays in the three colors are incident onto a single liquid crystal panel at mutually different angles, and are modulated by the single liquid crystal panel.

11. The optical display system of claim 1 , wherein a normal to a major surface of the at least one liquid crystal panel defines a tilt angle ψ of 1 degree to 15 degrees with respect to the optical axis of a principal light ray that has been emitted from the light source.

12. The optical display system of claim 1 , wherein the projection optical device includes a projection lens with an F value of lens than 1.8.

13. The optical display system of claim 1 , further comprising: a circuit for generating data representing multiple subframes from data representing a frame of an image to be formed by the projection optical device on a projection plane and getting the multiple subframes displayed on the at least one liquid crystal panel one after another time-sequentially; and an optical shifter for optically displacing on the projection plane, selected ones of the multiple subframes being displayed on the at least one liquid crystal panel.

14. The optical display system of claim 13 , wherein the optical shifter includes at least one shifting section that periodically displaces an optical axis of incoming light that has been incident on the shifting section, and wherein the shifting section comprises: a first liquid crystal cell, which changes a polarization direction of the incoming light from a first direction into a second direction, or vice versa, in response to a first voltage being applied to a liquid crystal layer of the first liquid crystal cell, the first and second directions being perpendicular to each other; a second liquid crystal cell, which changes the polarization direction of the light that has been transmitted through the liquid crystal layer of the first liquid crystal cell from the first direction into the second direction, or vice versa, in response to a second voltage being applied to a liquid crystal layer of the second liquid crystal cell; and a birefringent element, which changes its refractive indices according to the polarization direction of the light, wherein the first liquid crystal cell, the second liquid crystal cell and the birefringent element are arranged such that the incoming light enters the first liquid crystal cell first, is transmitted through the second liquid crystal cell next, and then leaves the second liquid crystal cell, and wherein the first and second liquid crystal cells are arranged such that a director in an intermediate portion of the liquid crystal layer of the first liquid crystal cell arid a director in an intermediate portion of the liquid crystal layer of the second liquid crystal cell cross each other at right angles.

15. The optical display system of claim 14 , wherein the liquid crystal layers of the first and second liquid crystal cells are made of TN mode liquid crystal materials having mutually opposite optical rotatory directions.

16. The optical display system of claim 14 , wherein the liquid crystal layers of the first and second liquid crystal cells are made of ECB mode liquid crystal materials.

17. The optical display system of claim 13 , further comprising at least one more shifting section that has the same structure and function as the shifting section.

18. The optical display system of claim 1 , wherein the liquid crystal panel further includes a second uniaxial optical compensator between the liquid crystal layer and the second biaxial optical compensator.

19. The optical display system of claim 18 , wherein if an index ellipsoid of the second uniaxial optical compensator has a, b and a axes as principal axes and if principal refractive indices on the a, b and c axes are na, nb and nc, respectively, the c axis is substantially parallel to a normal to a major surface of the second uniaxial optical compensator. the a and b axes are defined on the major surface of the second uniaxial optical compensator, and na=nb>nc is satisfied.

20. The optical display system of claim 18 , wherein an c axis of the second uniaxial optical compensator defines a tilt angle θ with respect to a normal to a major surface.

21. The optical display system of claim 20 , wherein the tilt angle θ defined by the c axis of the second uniaxial optical compensator with respect to the normal to the major surface is greater than 1 degree but smaller than 20 degrees.

22. The optical display system of claim 18 , wherein a total retardation of the first and second uniaxial optical compensator, which is given by d 1 t ·Δnac (where Δnac=nc−na and d 1 t is a total thickness of the first and second uniaxial optical compensators), satisfies 400 nm<−d 1 t ·Δnac<700 nm.

23. The optical display system of claim 18 , wherein a retardation of each of the first and second uniaxial optical compensator, which is given by d 1 ·Δnac (where Δnac=nc−na and d 1 is a thickness of the first or second uniaxial optical compensator),satisfies 100 nm<−d 1 ·Δnac<400 nm.